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Moles/Transcript
Transcript Text reads: The Mysteries of Life with Tim and Moby Tim and Moby are in a tunnel beneath the ground. Tim is picking at the tunnel wall with a pickaxe. Moby is studying a treasure map. Tim hits something solid. It is a treasure chest. He brushes dirt off of it. TIM: Awesome. That treasure map was right. The treasure chest opens. It is filled with gold, jewels, and a sheet of paper. Tim reads from a typed letter. TIM: Dear Tim and Moby, I need a way to explain a mole, Avogadro's number. Help. From, Jennifer. A mole pokes its head through the tunnel wall. Moby points at it. MOBY: Beep. TIM: No, I don't think she's talking about the animal. The mole grunts. TIM: In chemistry, a mole is a number used to count really tiny particles like molecules and atoms. Take this test tube. Tim holds up a test tube. TIM: Even though it's tiny, it contains so many air molecules that numbers like "trillion" or "quadrillion" don't even come close. The mole gives chemists an easy way to figure out how many molecules of a substance are in a sample, just by measuring its mass. An animation shows a smiling scientist pointing to a blackboard. The blackboard displays a drawing of a beaker and several molecules. TIM: If you think about it, we actually do this kind of counting all the time. For example, hardware stores often sell things like nails by weight. An animation shows a hardware store clerk weighing a bag of nails with a scale on his counter. TIM: They know how many nails there are per pound, so weighing a bag of them is just as good as counting. MOBY: Beep. TIM: What does this have to do with moles? Well, you know how the word "dozen" means "twelve" of something? An image shows an egg carton. Text on the carton reads: 1 dozen eggs. TIM: The mole also represents a set number6.02 times 10 to the 23rd power, or 602 with 21 zeros after it. Text reads: 1 mole eggs = 6.02 times 10 to the 23rd power eggs. MOBY: Beep. TIM: No, I did not just make that up. 6.02 times 10 to the 23rd is the result of a long series of brainstorms, starting with an Italian scientist named Amedeo Avogadro. An image shows Amedeo Avogadro next to a whiteboard. The whiteboard displays illustrations of beakers, a thermometer, and a barometer. TIM: In 1811, he proposed a groundbreaking concept. Equal volumes of different gases at the same temperature and pressure contain the exact number of molecules. Let's pretend that these emeralds are molecules of carbon gas, and these rubies are molecules of oxygen gas. Tim holds a handful of emeralds and a handful of rubies. TIM: Now let's say we fill two identical containers with each gas. An animation shows two identical glass beakers with measurements marked on their sides. TIM: According to Avogadro, if one container holds 20 emeralds, er, molecules, of carbon gas, then the second container will hold 20 molecules of oxygen gas. The beakers become full, one with green carbon molecules and the other with red oxygen molecules. Text beneath each beaker reads: 20. MOBY: Beep. TIM: Well, no. I just picked 20 randomly. See, Avogadro never figured out the actual number of molecules in any given volume of gas. Back then, scientists didn't have any way to measure a molecule's size or mass. An image shows a molecule. A question mark appears on the image. TIM: But over the next century, we learned much more about these tiny particles. For one thing, scientists pinned down the concept of atomic mass, the mass of a single atom. You can see the atomic mass of any atom on the periodic table, expressed in atomic mass units, or u. An image shows the Periodic Table of Elements. An animation gives an example of what Tim is describing, displaying text that indicates that the element Carbon has an atomic mass of 12.001 u. TIM: Then, in 1902, an incredible connection was made. Measure any element, in an amount equal to its atomic mass in grams, and you'll get the same number of atoms. Text on the Periodic Table indicates Carbon's weight of 12.001 grams. TIM: That number is the mole. Text reads: 12g = 1 mole. MOBY: Beep. Moby scratches his head. TIM: OK, think of it this way. Helium has an atomic mass of about 4 u. An animation shows a helium-filled balloon which turns into a clear beaker. Text on the beaker reads: He = 4 u. TIM: That means a four-gram sample contains one mole of helium atoms. Text beneath the beaker reads: 4g = 1 mole. TIM: Zinc has an atomic mass of about 65 u, which means a 65-gram sample contains one mole of zinc atoms. An image shows a bar of zinc. Text on the bar reads: Zn = 65 u. Text beneath the bar reads: 65g = 1 mole. The helium animation and the zinc image are displayed side by side. TIM: Different elements, different sized samples, but both have the same number of atoms. 6.02 times 10 to the 23rd atoms, to be exact. And it's not just for individual atoms. Any molecule can be measured in moles. MOBY: Beep. TIM: Well, it helps chemists make all sorts of practical calculations. Let's say you want to break down some water to get hydrogen. How much hydrogen will you get? Moby is in a laboratory, wearing a white lab coat and holding a beaker. Text on the beaker reads: H2O. An image shows a hydrogen atom. TIM: Easy. All you have to do is take the mass of the water and convert it to moles. So let's say you have one mole of water. Text beneath the beaker of water reads: 1 mole H2O. TIM: We know from water's chemical formula that there are two hydrogen atoms for every oxygen atom. An image shows a diagram of a water molecule with two hydrogen atoms and one oxygen atom. TIM: So, one mole of water contains two moles of hydrogen atoms and one mole of oxygen atoms. Text reads: 1 mole H2O = 2 moles H + 1 mole O. TIM: Using the relationship between moles and grams, you can figure out exactly how much hydrogen you'll get from any amount of water. Text beneath the equation reads: 1 mole H2O = 2 grams H + 16 grams O. TIM: On the flip side, if you know you need a certain amount of hydrogen, you can calculate precisely how much water needs to be broken down. And that, my friend, is just one example of what moles can do to help us. Chemists use molar equations every day to synthesize all kinds of useful stuff, from artificial sweetener to sunblock. An image shows two chemists in a lab doing the work that Tim describes. Images show artificial sweetener and a tube of sunblock. TIM: And it can tell us important things like, how much carbon dioxide will burning a gallon of gasoline produce? An animation shows exhaust clouds coming from a car's tailpipe. Text on the clouds reads: CO2. TIM: Anyway, I got some treasure burning a hole in my pocket. He turns to the mole, who is still watching him from a hole in the tunnel wall. TIM: How about helping us lug this stuff out of here, little guy? The mole nods. Then he moves himself next to the treasure chest and pulls it down through the tunnel's floor. TIM: Hey, our loot! The treasure chest is gone. Tim becomes angry and screams loudly at the mole. TIM: MMMMOOOOLLLLEEEE! Category:BrainPOP Transcripts Category:BrainPOP Science Transcripts